Seven liters! Four hundred and twenty-eight cubic inches in a Mustang! We were expecting a cataclysm on wheels, the automotive equivalent of the end of the earth. We were pleasantly surprised to discover that the GT 500 isn’t anything like that. The old corollary to that old adage, “There’s no substitute for cubic inches,” is “except rectangular money”–and who would know better than Carroll Shelby. When the Cobra 289 peaked out on the racetrack, there were several ways of making it go faster–most expensive, one cheap. One of the more expensive ways was the Daytona coupe body. The late Ken Miles found a better way. At Sebring in 1964, he shoehorned a Ford 427 NASCARized engine into a Cobra roadster. The experiment came to rest, sorely bent, against a palm tree, but Miles persisted. By the end of the season, at Nassau, he had another one bolted together. It blew up, but the die was cast. Early in 1965, Shelby announced the Cobra II with a 427 cu. in. V-8 replacing the 289. That June, at Le Mans, two of Ford’s rear-engined GT prototypes appeared with the big 427 instead of the 289. The Europeans hooted and jeered at the bulky, heavy, unsophisticated V-8 with its pushrods and single four-barrel carburetor. A year later, Ford 427s swept the first three places at the French classic, with Shelby’s two entries dead-heating the final lap. What the 427s had beaten was a team of 270 cu. in. Ferrari V-12s with multiple carburetion and four overhead camshafts. The Italian engine developed almost as much horsepower as the Ford–425 hp vs. 485–but it was much more tautly stressed and, therefore, fragile. Which is the whole point of 7-liter Fords, Cobras, and now, Shelby Mustangs.
For ’67, Ford offered the Mustang with their tried-and-true 390 V-8, which has a bore and stroke of 4.05 x 3. 78 inches. Ford also builds a 428 V-8 on the same block with a bore and stroke of 4.13 x 3.98 inches. Why not, reasoned Shelby, use this engine in the ’67 Shelby Mustang? Why not indeed. The car is called the GT 500 and its engine is called the Cobra Le Mans.
Please note that the Cobra Le Mans engine displaces 428 cubic inches. That sounds like a hair better than the 427. In fact, they are two entirely different engines. Both have the same external dimensions, but the 427 is more oversquare, with a bore and stroke of 4.23 x 3. 78. The 427 is a racing engine, full of the kind of intestinal fortitude that makes it capable of enduring 500 miles at Daytona and 24 hours at Le Mans. The 428 is a passenger-car engine, and nearly $1000 cheaper than the 427. Few people would be happy with the 427 unless they were racing it. It’s noisy, balky, and an oil burner at normal highway speeds. The GT 500 is not a racing car, although but for a few subtle differences its engine is the same as the one that propelled Shelby’s Fords to victory at Le Mans. Seven liters in a Mustang! The early GT 500 engineering prototype was the fastest car ever to lap Ford’s twisty handling loop, except for the GT 40s, of course. And the same car cut a quarter-mile in 13.6 seconds at 106 mph. Super car!
For 1966, Shelby toned the GT 350 down from a wild mustang to a merely high-strung thoroughbred. It was barely tame enough for the Hertz Corporation, which bought 1000 of them and put them into service as the hottest rent-a-cars the business has ever seen. The GT 350 still wasn’t acceptable to a large enough body of potential buyers, so, in 1967, an abrupt change in policy has transformed the Shelby Mustang. The $1000-or-so above the price of a comparable Mustang that used to go into expensive, unseen mechanical improvements is now lavished instead on exterior styling changes. The back lot at Shelby American’s remanufacturing plant is littered with stock Mustang front and rear sheet metal, and engine and trunk lids. In their stead go fiberglass panels stylized by Ford’s Chuck McHose, working in close co-operation with Shelby American. The new nose piece arches tautly forward, forming a deep cowling for the headlights (changed from duals to quads, with the high-beams centered in the grille, driving-lamp style). The hood features an air scoop even larger than last year’s, now divided by an air-splitter, and it’s still functional. At the rear, the new trunk lid and tail piece combine to form a racy-looking aerodynamic spoiler lip. No one would say for sure if high-speed tests had proved the efficiency of this styling gimmick or not—but it looks right. Finally, the side louvres have been replaced by scoops—big hairy scoops that poke out into the airstream beyond the boundary layer. Actually, these are to let the air out; stale interior air exits through the inconspicuous slot behind the scoop. The forward facing scoop leads to a narrow venturi area that helps draw air out the rear slot. That light behind the scoop flashes when the turn signals are on and glows steadily when the brakes are on. Another pair of funnel scoops are installed at the rear of the sculptured side panel—this time to blow air at the rear brake drums. A pair of giant taillights running almost the full width of the Kamm-inspired tail completes the Shelby look. As a whole, the Shelby Mustangs make the regular Mustangs look sick.